Pressure-resistant plastics bottle



May '12, 1970 0. LACHNER 3,511,401

PRESSURE-RESISTANT PLASTICS BOTTLE FilecIJuly 11, 1968 United States Patent 3,511,401 PRESSURE-RESISTANT PLASTICS BOTTLE Otto Lachner, Kempten, Allgau, Germany, assignor to Lever Brothers Company, New York, N.Y., a corporation of Maine Filed July 11, 1968, Ser. No. 744,020

Claims priority, applicatgrangGsermany, July 20, 1967,

Int. Cl. BdSd 1/40 US. Cl. 215-1 6 Claims ABSTRACT OF THE DISCLOSURE This invention relates to a pressure-resistant plastic bottle for carbonated drinks.

Pressure-resistant plastic bottles for beer and other carbonated drinks are already known in the traditional cylindrical glass-bottle shape and also in a shape consisting of several curved zones. In another known bottle a cylindrical main part tapers off at the bottom as a curved zone merging into the main part but forming an edge with a flat base, the radius of the curved zone being smaller than the radius of the cylindrical main part and the diameter of the surface on which the bottle stands not exceeding 90% of that of the cylindrical main part. These bottles have not been widely accepted, however, as they still have to have relatively thick walls and are therefore too expensive as non-returnable packs.

The region where the bottles are subject to most stress, from internal pressure, is at the bottom, and particularly at the zone of transition from the side wall to the base. For this reason bottles with slightly convex bases have been proposed. Since these bottles cannot stand on their bases, they have been provided with supporting rings or ribs or lug-shaped projecting parts. These shapes have not led to any considerable reduction in the amount of material required. Furthermore, bottles with projecting parts are not what the consumer usually expects a beer bottle to be like.

The aim of the invention is to find a form of the curved transition zone between the planar main part of a bottle and a non-convex base by means of which a pressureresistant plastic bottle can be made using a minimum of material.

Theoretical considerations and practical tests have revealed that in cylindrical bottles with flat bases and a curved transition zone between the planar cylindrical main part and the base, peak stresses occur at the points where the curved transition zone merges into the cylinder plane and into the base plane. The smaller the radius of curvature the greater are these peaks. In the tests increasing internal pressure caused the whole bottom portion to blow ofr, the break taking place, owing to the deformation that preceded it, in the region of the area where the transition zone merges with the cylinder plane. The break occurs at the same place in bottles with convex bases.

It has now been found that a particularly favourable distribution of the stress can be obtained if the radius of curvature changes by decreasing steadily in the curved zone of transition from the planar main part to the hottom, the smallest radius of curvature being at the contact line which the bottle base makes with a supporting surface on which it stands.

This smallest radius of curvature should, however, be as large as possible and the centre of curvature should be as near as possible to the longitudinal axis of the bottle, so that the diameter of the contact line is therefore relatively small. In order to achieve thi particularly favourable distribution of stress, the central portion of the base of the bottle is concavely recessed.

The curved transition from the cylindrical portion to the contact line therefore first takes place somewhat in the form of a hyperbola adjacent to a zone with said smallest radius of curvature. At the contact line of the base, a tangent to the smallest radius of curvature is at to the longitudinal axis of the bottle.

The above optimal conditions can, however, only be realized in practice within certain limits, as the bottles must be steady enough not to fall over in the bottling machine or when it reaches the consumer. A bottle falls over if its contact surface is too small in diameter and a vibration throws it off balance, or if the bottom bulges outwards due to an increase in internal pressure. The deformations occurring in plastic bottles as a result of an increase in internal pressure must therefore also be taken into consideration.

Allowing for these aspects the plastic bottle according to the invention, made in particular of PVC and preferably of rigid PVC, has been developed. Owing to the shape of it curved'transition zone and base, while being sufiiciently resistant to pressure and steady for carbonated drinks, it enables an extraordinarily low weight of material to be used. The central portion of the base is concavely recessed. The inventive feature of the bottle is that the weight of material used is only 1.25 to 2.5 grams PVC per cm. of bottle height, in particular 1.5 to 2.2 grams PVC per cm., of bottle height, and it has a curved transition zone the height of which is greater than or equal to 0.4 times the maximum diameter of the bottle in the planar main part, preferably 0.4 to 0.6 times, and the radius of curvature of which changes by decreasing steadily from the transition from the planar main part to the contact line of the base, at which contact line the radius of curvature is 0.15 to 0.3 times, preferably 0.17 to 0.2 times, the diameter of the bottle, and the diameter of the contact line being 0.4 to 0.7 times, preferably 0.5 to 0.6 times, the diameter of the bottle. In the upper part of the curved transition zone the radius of curvature adjacent the planar main part is less than infinity and then changes by decreasing steadily while still remaining greater than or equal to the maximum diameter of the planar main part of the bottle. Preferably the radius of curvature adjacent the planar main part is at least twice the maximum diameter of the planar main part, and changes by decreasing steadily until it is not less than equal to said maximum diameter.

The concave recess in the central portion of the bottle base has a height of 0.04 to 0.3 times, preferably 0.045 to 0.1 times, the maximum diameter of the planar main part of the bottle.

The curved transition zone and the base of the bottle, and preferably the other parts too, are axially symmetrical. The curvature of the transition zone and base according to the invention can, however, also be used for bottles the planar main part of which is not cylindrical but pear-shaped, oval, angular. If the main part of a bottle is not cylindrical in shape, the diameter to which the other dimensions are related is the maximum diameter perpendicular to the bottle axis.

Because of the combination of measurements for the curved transition zone and the base according to the invention, it is possible to manufacture blown pressureresistant plastic bottles using a surprisingly low weight of material. For cylindrical bottles of a conventional size such as one-third of a litre, an adequate weight of material is 1.8 to 2.1 grams per cm. of bottle height, preferably about 2.0 grams per cm. of bottle height. The advantage of the new form of the base and transition zone is that if the internal pressure increases, the bottom of the bottle can change shape without bulging outwards to any great extent. Depending on the internal pressure a state of equilibrium is established with a corresponding height of the concave recess in the bottle base. As the internal pressure increases the height of the recess decreases, which has a favorable effect on the distribution of stress. The diameter of the contact line of the base is not changed to such an extent, however, that the steadiness of the bottle is affected.

The shape of bottle according to the invention is described again with the aid of the accompanying drawing, which shows a cross-section of an axially symmetrical bottle.

The bottle consists essentially of a planar cylindrical main part 1, a curved transition zone 2, a curved bottom zone 3, a neck 4 and a mouth 5. In the cylindrical main part 1 the bottle has a diameter D to which all the other preferred dimensions according to the invention are related. The curved transition zone 2 has a height H which is equal to or greater than 0.4 D, preferably 0.4 to 0.6 D. The curved transition zone 2 is somewhat in the form of a hyperbola in that it has a changing radius r which adjacent its transition from the cylindrical main part 1 has a radius of curvature less than infinity, preferably 2 D and said radius of curvature r changes gradually by decreasing steadily until the value of r becomes not less than D as the curved transition zone descends and becomes of a radius of curvature r at the bottom zone 3, which is 0.15 to 0.3 D, preferably 0.17 to 0.2 D.

The bottle stands on a circular contact line a of diameter d which lies between 0.4 and 0.7 D, preferably 0.5 to 0.6 D.

The bottom zone 3 includes a concave recess in the central portion of the base, the height h of this concave recess being 0.04 to 0.3 D, preferably 0.045 to 0.12 D.

The bottle depicted in the drawing at full size holds 0.33 litres, is 160 mm. high, has a diameter D of 68 mm., and weighs approximately 30 grams (1.87 grams per cm. of bottle height). Other values are as follows:

H is 30 mm. (0.44 D);

d is 38 mm. (0.56 D);

n is 10.5 mm. (0.15 D);

The change of radius of curvature r is a decrease from 2 D to D; r is 10.5 mm. (0.18 D) I claim:

1. In a pressure-resistant plastic bottle for carbonated liquids having a wall with a planar main part contiguous with a curved transition zone which merges into a curved bottom zone, the combination of features which provide that; the weight of material used is 1.25 to 2.5 grams per centimeter of bottle height; the curved transition zone of the wall is somewhat in the form of a hyperbola and has a height which is equal to or greater than 0.4 times the maximum diameter of the bottle in the planar main part; the redius of curvature of said curved transition zone is less than infinity adjacent the planar main part and changes by decerasing steadily while still remaining greater than or equal to the maximum diameter of said planar main part; the curved bottom zone merges into a curved base which has a concave central recess and also a circular contact line to engage a supporting surface on which the bottle stands, the radius of curvature of the bottle wall at said contact line being 0.15 to 0.3 times the maximum diameter of the planar main part; and the diameter of said contact line of the bottle base is 0.4 to 0.7 times the maximum diameter of the planar main part of the bottle wall.

2. The bottle according to claim 1, wherein the weight of material used is 1.5 to 2.2 grams per centimeter of bottle height.

3. The bottle according to claim 1, wherein the concave central recess in the curved base has a height of 0.04 to 0.3 times the maximum diameter of the planar main part of the bottle wall.

4. The bottle according to claim 3, wherein the height of the concave recess is 0.05 to 0.1 times the maximum diameter of the planar main part of the bottle wall.

5. The bottom according to claim 4, wherein the radius of curvature of the curved transitition zone adjacent the planar main part is twice the maximum diameter of the planar main part, and changes by decreasing steadily until main part, and changes by decreasing steadily until it is not less than equal to said maximum diameter.

6. The bottle according to claim 5, wherein the curved transition zone of the bottle wall has a height of 0.4 to 0.6 times the maximum diameter of the planar main part of the bottle wall.

References Cited UNITED STATES PATENTS DONALD F. NORTON, Primary Examiner US. Cl. X.R. -.5

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No 3, 511 401 Dated May 12 970 Invent0r(s) Otto Lachner It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

In the Claims:

Claim 1, line 10, change "redius" to -radius--.

Claim 1, line 12, change "decerasing" to -decreasing--.

Claim 4, line 2, change 0.05" to --0.045--.

Claim 5, line 2, change "transitition" to --transition-.

Claim 5, lines 4 and 5, delete "and changes by decreasing steadily until main part,".

(SEAL) Attest:

Edward M. Fletcher, 1

Attesting 0m mm: 1:: 31:.

Commissioner of Patents FORM PO-IOSO (10-69) USCOMM DC man P u s covsmmnn Imurmr. orncs Ill! o1n-114 

